MIDI protocol

MIDI Protocol

Musical Instrument Digital Interface

MIDI Messages

Estructurados por grupos de 8 bits (un byte) los mensajes MIDI tienen dos tipos de datos.

MIDI commands

MIDI data

0111 1111

1111 1111

There is MIDI all over the place

We can distinguish between MIDI commands and MIDI data by looking at the message’s most significant bit (msb: the leftmost bit).

• The MIDI Commands are distinguished by a 1 at their msb.
• In contrast, MIDI data have a 0 as their msb.

What kind of messages does MIDI produce?

• Web browsers implement MIDI
• Mobile devices can use MIDI
• All computers can use MIDI

What is MIDI?

• Symbolic representation of music.

60 is a middle C

increment chromatically

so C# is

61

and the next C is

60 + 12 = 72

MIDI is a communications protocol that allows the interconnection between different kinds of musical devices, controllers and software applications.

The MIDI protocol does not transmit sound, it only transmits the necessary control data to manipulate sound producing devices.

MIDI does not describe the timbre of an instrument, rather it is a common language that can be used to communicate between different modules.

The MIDI protocol implements a scheme of messages as it is described in a document known as the MIDI 1.0 Detailed Specification.

What can you do with MIDI?

Examples of MIDI messages

Command Meaning # parameters param 1 param 2

0x80 Note-off 2 key velocity

0x90 Note-on 2 key veolcity

0xA0 Aftertouch 2 key touch

0xB0 Continuous 2 controller # controller value

controller

0xC0 Patch change 1 instrument #

0xD0 Channel 1 pressure

Pressure

0xE0 Pitch bend 2 lsb (7 bits) msb (7 bits)

0xF0 (non-musical commands)

• Control virtual instruments
• Produce complex compositions
• Store performances in your hard drive
• Design your own interfaces
• With GM you can instantly play back pre-recorder music.

Controllers

Example of a typical MIDI setup

There are several types of controllers

MIDI Messages

Control Change (CC):

These messages can control the values of singles parameters that define how a synthesizer sounds.

MIDI Commands

Two parts

System Exclusive Messages:

Used to communicate things that are specific for a given device.

command

channel

1000 Note Off

1001 Note On

1010 Aftertouch

1011 Continuous controller

1100 Patch change

1101 Channel Pressure

1110 Pitch bend

1111 (non-musical commands)

from

1 to 16

but given

that the

representation

is binary, they

go from

0 to 15

MIDI Messages

Sequencers

Program Changes:

Selects sounds in another device

MIDI Jacks

• A sequencer can record a MIDI performace.
• You can create projects with several tracks and instruments.
• You can correct an modify the data recorded in a track
• Quantization
• Transposition
• Scaling

Standard MIDI Files

• Recordings can be saved in Standard MIDI Files (SMF).
• SMF offer a quick solution to share MIDI performances and get MIDI tracks from other artists or known music.

Duplex

Master - slave

MIDI Messages

Devices with multiple output ports

Daisychaining

(may cause dalay)

MIDI patchbay

MIDI USB

General MIDI

Performance:

• Note on
• Note off
• Velocity
• Pitch bend
• After touch

• A standard set 128 of sounds organized by number.
• Lets you produce a composition that can be played right away in any MIDI capable machine, mantainning the instrumentation.
• General MIDI can be recognized by its logo.

General MIDI 2

MIDI Connections

General MIDI 2 is an extended version of General MIDI.

DIN 5

MIDI Channels

Each connection can transport up to 16 different channel MIDI data

You can control up to 16 devices from a computer or 16 different instruments in the same device